A Reagan White House political director, former chairman of both the Republican National Committee and the Republican Governors Association and namesake of the white-shoe lobbying outfit BGR Group, Barbour could have raised millions with one pass through his Rolodex.

Now, it’s not clear whether any Republican not named Romney will be able to capture the broad establishment support and cash that would have gravitated naturally to Barbour.

If Daniels enters the race, Republicans say, his friendship with Barbour and his own long D.C. track record would make him the favorite to win over the class of political professionals who have proved so influential in past GOP presidential primaries.

But there’s no guarantee Daniels will run for president — or that if he does run, he’ll be able to capture 100 percent of Barbour’s support in Washington and across the country.

“There’s a political class in Washington and around the country that, if Haley was going, they were going to be with him,” explained Tom Reynolds, former New York congressman and former National Republican Congressional Committee chairman.

“If Mitch Daniels is going to run, he is the greatest beneficiary of Haley not running,” said Reynolds, who now works at the law and lobbying firm Nixon Peabody. “If Mitch Daniels doesn’t run, it will get sprinkled across the entire campaign field.”

Daniels has sent ambiguous signals about the race but has long been clear that he would prefer not to run against his longtime friend and former Reagan White House colleague. The Hoosier issued a statement on Barbour’s decision Monday saying he would “have been proud to try to help [Barbour] had he chosen to run.”

Advisers to Barbour said he won’t make any immediate moves toward another candidate, but one noted that Daniels is his “closest political friend.” In a December interview with POLITICO, Barbour said flatly: “If he runs and I don’t, I can’t imagine myself supporting anybody else.”

But Charlie Black, the longtime Republican operative and lobbyist, questioned whether even the Indiana governor can unite Barbour’s supporters under a single banner.

“It never happens that way,” said Black, who’s supportive of Daniels. “If Haley decided to get involved and endorse somebody and tried to bring those people with him, he could get a lot of them. But you wouldn’t get them all.”